Hi I just planned a 4th order bandpass box for this sub:

WoofersEtc.com - REF-TM12.2 - 12" Tidal Audio Subwoofer Dual 2 Ohm OEM by Image Dynamics

Nominal Impedance (IMP) 1/4 ohms
DC Resistance (Re) .98 / 3.8 ohms
Resonant Frequency (Fs) 20.7 Hz
Electrical "Q" (Qes) .412
Mechanical "Q" (Qms) 3.80
Total "Q" (Qts) .372
Equivalent Volume (Vas) 5.71 cu. ft.
One Way Linear (Xmax) 17.0 mm
Cone Area (Sd) 545 cm2
Sensitivity (Spl) 88.6db
RMS Power Handling (Pwr) 50 to 400W RMS
Speaker Displacement .07 cu. ft.
Mounting Depth: 6"
Mounting Diameter: 11"

I was wandering if a 39 square inch port area would be big enough. Its a 13 per 3 inch port slot.